Changed socket listening to be optional.
ImageEditor extending PlotImageEditor for better maintenance, and
replaced plottingSystem with getPlottingSystem().
Adjusted positions of splash screen.
Fixed splash screen.
Commented out ReUseEditor in File Explorer because it is contributed
from File Navigator, and no need 2 at the same time.
Added clone_el.gif to icons.
Merge branch 'master' of github.com:DawnScience/embl-cca